Fix Platform.localeName by setting _Platform._localeClosure (#4450)

lib/ui/dart_runtime_hooks.cc

@@ -112,16 +112,20 @@ static void InitDartAsync(Dart_Handle builtin_library,
                                &schedule_microtask));
 }
 
-static void InitDartIO(const std::string& script_uri) {
+static void InitDartIO(Dart_Handle builtin_library,
+                       const std::string& script_uri) {
+  Dart_Handle io_lib = Dart_LookupLibrary(ToDart("dart:io"));
+  DART_CHECK_VALID(io_lib);
+  Dart_Handle platform_type =
+      Dart_GetType(io_lib, ToDart("_Platform"), 0, nullptr);
+  DART_CHECK_VALID(platform_type);
   if (!script_uri.empty()) {
-    Dart_Handle io_lib = Dart_LookupLibrary(ToDart("dart:io"));
-    DART_CHECK_VALID(io_lib);
-    Dart_Handle platform_type =
-        Dart_GetType(io_lib, ToDart("_Platform"), 0, nullptr);
-    DART_CHECK_VALID(platform_type);
     DART_CHECK_VALID(Dart_SetField(platform_type, ToDart("_nativeScript"),
                                    ToDart(script_uri)));
   }
+  Dart_Handle locale_closure = GetClosure(builtin_library, "_getLocaleClosure");
+  DART_CHECK_VALID(
+      Dart_SetField(platform_type, ToDart("_localeClosure"), locale_closure));
 }
 
 void DartRuntimeHooks::Install(IsolateType isolate_type,
@@ -131,7 +135,7 @@ void DartRuntimeHooks::Install(IsolateType isolate_type,
   InitDartInternal(builtin, isolate_type);
   InitDartCore(builtin, script_uri);
   InitDartAsync(builtin, isolate_type);
-  InitDartIO(script_uri);
+  InitDartIO(builtin, script_uri);
 }
 
 // Implementation of native functions which are used for some

lib/ui/hooks.dart

@@ -39,6 +39,12 @@ void _updateWindowMetrics(double devicePixelRatio,
   _invoke(window.onMetricsChanged, window._onMetricsChangedZone);
 }
 
+typedef String LocaleClosure();
+
+String _localeClosure() => window._locale.toString();
+
+LocaleClosure _getLocaleClosure() => _localeClosure;
+
 void _updateLocale(String languageCode, String countryCode) {
   window._locale = new Locale(languageCode, countryCode);
   _invoke(window.onLocaleChanged, window._onLocaleChangedZone);

runtime/dart_vm_entry_points.txt

 dart:_internal,::,_printClosure
 dart:async,::,_setScheduleImmediateClosure
 dart:io,::,_setupHooks
+dart:io,_Platform,_localeClosure
 dart:io,_Platform,set:_nativeScript
 dart:isolate,::,_getIsolateScheduleImmediateClosure
 dart:isolate,::,_setupHooks
@@ -12,6 +13,7 @@ dart:ui,::,_dispatchSemanticsAction
 dart:ui,::,_drawFrame
 dart:ui,::,_getGetBaseURLClosure
 dart:ui,::,_baseURL
+dart:ui,::,_getLocaleClosure
 dart:ui,::,_getMainClosure
 dart:ui,::,_getPrintClosure
 dart:ui,::,_getScheduleMicrotaskClosure